U.S. Pat. Nos. 4,861,958 and 4,678,882 describe a popcorn popping container in the form of a paperboard cup with a microwave lossy element added to the bottom of the cup either as a separate disc or as a laminate and with a lid having appertures for releasing moisture produced during popping. While the lossy element is intended to assist in popping the corn, neither the volume of popped corn produced nor the percentage of unpopped kernels have been as good as desired. Users are particularly disturbed when a substantial number of unpopped kernels or "old maids" remain after the popping process. It is therefore one object of the invention to make an improvement in the volume of popped corn and unpopped kernels produced in a package having the general form described in the aforesaid patents.
U.S. Pat. No. 4,586,649 describes a poping package in which the bottom of the package slopes centrally toward a central panel of small size. The carton resembles two truncated pyramids which are joined base-to-base and supported on a separate stand in the form of a collapsible tube. The sloping lower portion of the carton causes the corn to bunch together in a clump. In addition, the supporting stand must be manipulated by hand. This requires extra attention by the user and in the present state of development of the art is considered to be unsatisfactory because of the extra time, care and attention needed in setting up the package for popping. Moreover, many users have trouble following directions. Popping will be less satisfactory because the package also contains no susceptor. Finally, the distance between the package and the floor of the oven varies from one point to another because the bottom part of the package is sloped.
It is also known to provide a foil pan with an expandable cover for popping popcorn on a stove top. These packages are not suitable for use in a microwave oven because the metal foil pan acts as a shield. Examples are U.S. Pat. Nos. 3,519,439; 3,782,976 and 3,969,535.
Another popcorn package is described in U.S. Pat. No. 4,584,202. This package includes a paperboard carton with a top panel having a removable portion that is detached from the rest of the package just prior to popping. The unpopped popcorn is placed in a separate pouch which as it expands is pushed outside the carton through the top opening. The package contains no susceptor, and accordingly, popping of the corn will proceed at a relatively slow rate and may be incomplete. The use of a separate inner pouch makes the container more expensive. By now, the art has developed to a point at which the removal of a panel prior to popping is a deficiency that may render the product unacceptable to some users. In the course of developing the present invention it was found that the large bubble of superheated steam which collected under the flexible cover could burn the fingers when the package was opened. An attempt was made to vent the steam through vent holes. Vent holes, however, allow moisture to enter the corn and reduce popping performance. Moisture could also enter to a degree even without vent holes. Changes in corn moisture due to the gain or loss of moisture from the atmosphere was found to be a troublesome obstacle to good popping performance, both with respect to the number of unpopped kernels remaining as well as the volume of popped corn produced.
It is therefore a major object of the invention to provide an improved microwave popping package which requires no manipulation prior to use, from which popped corn can be eaten directly, which is capable of being stacked one inside another, and which provides a substantial improvement both in the volume of popped corn produced and also in the number of kernels that remain unpopped. A further object is to provide a popping package of the type described having a microwave interactive susceptor material distributed in heat conductive relationship with the popcorn and to find a way to strategically locate the entire susceptor in relationship to the supporting surface of the oven. Another object is to provide a spacing or gap between the susceptor and the oven floor that is related to the electrical characteristics of the oven for maximum energy transfer to the susceptor. It is also an object to find a way to provide a reliable hermetic seal for the corn to promote good popping of the corn as well as to vent steam without allowing moisture to enter the food through the vent holes.
These and other more detailed and specific objects of the invention will be better understood by reference to the following detailed description and figures which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims.